The butterfly, the fly kick is very important, also.

在蝶泳中，打腿也非常重要。

Fly kick is very important, particularly in a 25 yard pool.

蝶泳腿非常重要，特别是在25码的短池中。

Or you can use the fly kick for you can always kick to the surface.

因为你总可以靠打蝶泳腿浮出水面，所以你要充分利用蝶泳腿。

This is very important for every age to work on the fly kick underwater.

对于任何年龄组的人来说，进行水下海豚腿的练习都是非常重要的。

Because the vertical fly kick is where you get the frequency or speed of kick.

因为立蝶能提高打腿的频率或者说打腿的速度。